Early detection of cell activation by ATR-FTIR spectroscopy

1. A method for detecting a cellular response resulting from a defined treatment or exposure, comprising

(a) depositing a sample comprising a plurality of cells under reaction conditions on an internal reflection element (IRE);

(b) directing a beam of infrared (IR) radiation through the IRE under conditions such that the IR radiation interacts with the plurality of cells;

(c) recording an absorption spectrum over a range of preselected frequencies; and

(d) comparing the absorption spectrum to a control spectrum;

wherein a change in absorbance at one or more frequencies compared to the control spectrum is an indication of a cellular interaction in the plurality of cells; and

wherein the reaction conditions comprise contacting the plurality of cells with a sample comprising one or more potential pathogens, allergens, or ligands.

2. The method of claim 1 , wherein the potential pathogen is a virus, bacteria, or yeast.

3. The method of claim 1 , wherein the potential ligand is selected from the group consisting of antibodies, growth factors, cytokines, chemokines, hormones, extracellular matrix proteins, and cell-surface proteins.

4. The method of claim 1 , wherein the potential ligand is selected from the group consisting of proteins, peptides, peptide nucleic acids, and small molecules.

5. The method of claim 1 , wherein the reaction conditions further comprise a change in temperature, pH, salinity, or any combination thereof.

6. The method of claim 1 , wherein the cellular interaction is detected within 15 minutes to 75 minutes.

7. The method of claim 1 , wherein the plurality of cells comprise bacterial or yeast cells.

8. The method of claim 1 , wherein the plurality of cells comprise mammalian cells.

9. The method of claim 1 , wherein the plurality of cells comprise a transformed cell line.

10. The method of claim 1 , wherein the range of preselected frequencies is between 50 cm −1 and 3700 cm −1 .

11. The method of claim 10 , wherein the range of preselected frequencies is between 800 cm −1 and 1500 cm −1 .

12. The method of claim 1 , wherein the IRE is an attenuated total reflectance (ATR) crystal comprising an optical material with a higher refractive index than the sample comprising the plurality of cells.

13. The method of claim 12 , wherein the IRE comprises a germanium crystal or a zinc selenide crystal.

14. The method of claim 1 , wherein the IR radiation that interacts with the plurality of cells is an evanescent wave with an average penetration depth of about 2 μm.

15. The method of claim 1 , further comprising Fourier transformation of the absorbance spectrum.

16. A method for using cells as a biosensor, comprising:

(a) exposing a homogeneous population of cells with a sample;

(b) depositing the homogeneous population of cells on an internal reflection element (IRE);

(c) directing a beam of infrared (IR) radiation through the IRE under conditions such that the IR radiation interacts with the plurality of cells;

(d) recording an absorption spectrum over a range of preselected frequencies; and

(e) comparing the absorption spectrum to a control spectrum;

wherein a change in absorbance at one or more frequencies compared to the control spectrum is an indication of a cell activating agent in the sample; and

wherein the cell activating agent comprises one or more potential pathogens, allergens, or ligands.

17. A system for detecting a cell activating agent in a sample, comprising:

(a) a Fourier transform infrared spectrometer configured with an internal reflection element (IRE) for attenuated total reflectance (ATR); and

(b) a homogeneous population of cells selected to react with the cell activating agent; and

wherein the cell activating agent comprises one or more potential pathogens, allergens, or ligands.